Old Galactic Standard started as a slang or jargon of traders and spacers, based on a mix of earlyHuman languages, Durese, and Bothese. Because of its popularity with members of those professions, its popularity and acceptance spread. Old Galactic Standard was later further influenced by Dromnyr, resulting ultimately in the standard Basic.

Most sentient species that made galactic contact could and did speak Basic in addition to whatever native or regional language they might have used on a daily basis. Some beings normally did not possess the organs necessary to speak Basic, including Polis Massans, Ssi-ruuk, P'w'ecks, Wookiees, and a number of insectoid races. Most Gamorreans could not speak Basic, though there were exceptions (such as GovernorKugg.) Whether or not a being could speak Basic, it was usually in their best interest to comprehend it, and most did.

The Towanis taught the Ewoks a mysterious and undocumented language, which did not help them understand Leia Organa, and later, Han Solo and Luke Skywalker, all of whom spoke Basic. The relation of that language to Basic is not known.

High Galactic was a dialect intended for displaying reverence and honor to religious figures.

Corellian accent—exemplified by Han Solo and Wedge Antilles. It was distinct enough so that a Corellian could instantly recognize another Corellian's speech.

Concord Dawn inflection—as exemplified by members of the Fett family. This was the most common accent among Mandalorians (perhaps due to the influence of their native language, Mando'a), with the tendency to pronounce words that had an 'e' with an 'i', e.g. word - delta, pronounced - dilta.

High Coruscanti—a more refined style of the Coruscanti accent. It was very posh and clipped and conveyed a sense of upper-class sensibility. The accent may also be faked to sound more important.[1]

Eriaduan accent—as exemplified by Grand Moff Tarkin. It might have simply been an artifact of the heavy influence of Coruscant, or "standard" language throughout the Core Worlds, and by implication, the elite of society, since people in the Colonies and Outer Rim spoke differently.

Yoda's dialect—an unusual form of Basic utilized by Jedi Grand Master Yoda and others of his tridactyl species, including Yaddle; it was characterized by an object-subject-verb format. However, another member of this species, Vandar Tokare, did not use this dialect.

Towani family dialect—this they taught to the Ewoks when they crashed on Endor. However it was not enough for those creatures to understand standard Basic a year later, when they met Princess Leia, Han Solo, Luke Skywalker, C-3PO, R2-D2 and the rest of the rebels.

Of interesting note, the Wookiee Ralrracheen spoke with a speech impediment. Due to the differences in the vocal abilities of Ralrra, his dialect was perfectly understandable by non Wookiees, and it was further suggested that some Wookiees with this condition could speak Basic, at the loss of all forms of Shyriiwook.

Basic-speaking Rodians tended to suffer from speech impediments as well, most notably a lisp. Avaro Sookcool and Teeloo were two such Rodians; the syllables R, L, and S proved to be the most problematic to vocalize.[2][3][4]

In translations into non-English languages, Basic is assumed to be English but translated to the other language.

While the letters are different in Basic than English, there are multiple examples where Latin alphabet letters are mentioned, such as in Obi-Wan-Kenobi's quote "Do you have a plan B?",[5] Mission Vao's habitual reference to Zaalbar as "Big Z",[6] and most droid designations. Greek letters are used at times, examples including Delta Squad.

Dialects in English correspond to different in-universe accents in the movies. Ewan McGregor's and Ian McDiarmid's faint upper-class Scottish accents are, for example, Coruscanti accents in the movies. As a general rule, Imperial characters have English accents while Rebels usually have Californian accents. However, it would seem that this is perhaps a representation of social class, as stormtroopers and other low-ranking Imperials are heard to speak with American accents, and some Rebels in English accents (Mon Mothma, for instance). Other accents are also heard, such as:

Star Wars authors have coined original English-like words derived from real English elements but which don't exist in the English language; they seem useful to a space-driven civilization of the Star Wars characters, but totally useless for our daily language. Such words are 'speciesism' (equivalent to racism, but against sentient beings other than the speakers), 'gentlebeing' (equivalent to gentleman, but applicable to all species, including non-humanoid ones), 'offworlder', 'bird' (slang for spaceship, cf. how US Navy slang calls 'torpedo' as 'fish'), 'hyperspace', 'homeworld', 'spacer', 'sentientologist', 'youngling' (young + suffix -ling meaning 'person') and other technological terms like blaster, midi-chlorian, droid (from android), durasteel, astrogation etc.

However, Basic vocabulary includes some totally original, of unexplainable etymology, words also unrelated to English, like Moff, Jedi, Padawan, Darth etc. or even compounds like Twi'lek ("twin lekku"). It is possible that such words are derived from other languages.